This invention generally relates to an instrument and method for surgical ligation of anatomical structures within a human or animal body. In particular, the instrument relates to ligation of reproductive tubes in the female or male anatomy to effect sterilization. The instrument places one or more elastomeric rings around the desired anatomical structure to bind, sever, or occlude the structure.
For example, under certain circumstances, a surgeon may need to sever or occlude the fallopian tubes of a female patient. The fallopian tubes may be severed according to various known procedures, including ligation through suturing the tubes, electrosurgical cauterization, and occlusion through a clip. These procedures are not satisfactory because they involve significant risk of infection or unintended damage to tissue, and they suffer from certain other disadvantages, as well. For example, a clip procedure may dislodge from the tubes with time. With electrosurgical sterilization, it is well-documented in the literature that unintentional burns can be inflicted on other organs, such as the bowel. Other procedures may require multiple entries of a surgical instrument through an incision, compounding the risk of infection or injury to the patient, and making the procedure unnecessarily complicated.
Because of these and other problems, ring applicator devices were developed that are inserted through channels on the order of ten millimeters in diameter. These devices have an inner cylinder slideably disposed in an outer cylinder. Grasping means are slideably disposed in the inner cylinder. The grasping means retracts a section of fallopian tube into the opening at the distal end of the inner cylinder. An elastic ring that has been placed circumferentially over the end of the inner cylinder is pushed by the outer cylinder off the inner cylinder and over the fallopian tissue extending from the opening in the inner cylinder's distal end. The ring binds around the tissue creating a u-shaped knuckle. A tightly fitted ring cuts off blood flow to the knuckle causing necrosis of the knuckle section of the tissue. This results in a sectioning of the tube, rendering the patient sterile. U.S. Pat. No. 4,085,743 to Yoon and U.S. Pat. No. 4,226,239 to Polk et al describe certain devices that deliver rings in the foregoing procedure.
Ideally, the devices used in minimally invasive surgical procedures should be insertable through the smallest possible incision. Devices are known that can be accommodated through eight-millimeter insertion channels. However, current demand is for medical instruments that may be inserted through even smaller channels. Smaller channels reduce the risk of infection and injury to anatomical structure, allow more precise surgery, and minimize trauma and scarring. The current demand in the surgical art is for surgical instruments that can be passed through insertion channels of five millimeters or less--as trends continue. Unfortunately, the known ligation instruments have not yet been adapted to fit or perform adequately in channels of about this size.
Simply scaling down existing devices does not solve the problem: the minimum size of the channel through which existing devices can be inserted first depends on the minimum cylinder diameter needed to accommodate the bulk size of the tissue to be retracted. The outer diameter of the outermost cylinder is added to this plus the outer diameter of the elastic ring that extends beyond the outer diameter of the outermost cylinder.
For example, the outer diameter of the straight-shaft cylinders used in prior art devices such as shown in U.S. Pat. No. 4,226,239 patent is generally about 6-8 mm. When the extending outer diameter of an elastic ring placed on the device is added to this, an insertion channel of at least about 8 mm is required. For these reasons and others, prior art devices have not been adapted to fit or perform adequately within channels approaching 5 mm or less.
The prior art devices also generally require at least three or more shafts concentrically and slideably disposed relative to each other. Under some circumstances, it is desirable to reduce the number of parts. This might hold true, for example, from the standpoint of manufacturing a low-cost, disposable device.
Existing devices also do not adequately address the problem of too forceful retraction of tissue into the relatively narrow recess of the instrument. Overly forceful retraction can damage sections of tissue unnecessarily. For example, if the damage to Fallopian tissue is severe enough, complications may arise, such as bleeding, scarring, and infection, which sometimes require re-surgery. The damage may also make reversal of the sterilization procedure impossible, foreclosing an important option to the patient. Accordingly, there is a need for instruments that reduce the risk of unintended damage to tissue being retracted.